Pollution of water by chlorinated hydrocarbons has become an important environmental problem and contaminated groundwaters represent a large portion of environmental remedial action plans throughout the world.
Dechlorination of trichloroethylene by elemental iron to generate reaction products such as ethylene, ethane, and chloride ion is known. The ability of iron to dechlorinate trichloroethylene offers a method for in situ treatment of groundwater. Additionally, the use of iron affords little environmental threat. Thus, it is desirable to be able to efficiently dechlorinate groundwater contaminates in situ using iron.
It is known that batch reactions using elemental iron typically require twenty to twenty-five grams of iron metal per hundred milliliters of aqueous sample containing twenty-five parts per million trichloroethylene. Half-lives for such reactions under buffered conditions range from five to twenty hours dependent upon the pH, type or source of elemental iron, surface area of iron, etc.
A commonly owned, copending application, titled "Enhanced Remediation of Aqueous Compositions Contaminated with Halogenated Hydrocarbons," discloses a method which reductively reacts chlorinated hydrocarbons with metallic iron in the presence of citric acid to generate innocuous byproducts. It is disclosed that lower amounts of iron, in the order of two grams per twenty-five parts per million trichloroethylene in a hundred milliliter sample, are required for the dechlorination of trichloroethylene in the presence of as little as one weight percent of citric acid based upon the weight of iron. By adding citric acid to the reaction solution, the rate of the dechlorination reaction is substantially increased, while the amount of iron needed to completely dechlorinate the hydrocarbons is reduced.
It was recently discovered that a homogeneous reaction can take place in solution between a preformed ferrous citrate complex, Fe (II) citrate, and trichloroethylene to generate chloride ion and rapid degradation of trichloroethylene to innocuous products. The ferrous citrate complex increases the efficiency of the dechlorination of hydrocarbons in aqueous solutions by significantly decreasing the amount of iron needed in the reaction.
Thus, it is an object of this invention to disclose a method to degrade chlorinated hydrocarbons in an aqueous media using a soluble iron (II) species.
It is a further object of this invention to use ferrous citrate to lower the oxidation potential of the Fe(II)/Fe(III) couple to allow favorable oxidation by trichloroethylene.